Which is an everyday situation for the math expression with the context provided?

; sharing something equally

A.
Cory had 150 dollars in his savings account. He withdrew K dollars to buy a catcher's mitt. He then had dollars left in his savings account.

B.
The cafeteria has a capacity of 150 seats. If k is the number of people in the cafeteria at lunch time, then is number of seats that were not used at lunch time.

C.
A librarian had 150 books to be placed on shelves with an equal number of books on each shelf. If k is the number of shelves to be used, then is the

Question

Which is an everyday situation for the math expression with the context provided?
 
  ; sharing something equally
 
 A.
Cory had 150 dollars in his savings account. He withdrew K dollars to buy a catcher's mitt. He then had   dollars left in his savings account.
 
 B.
The cafeteria has a capacity of 150 seats. If k is the number of people in the cafeteria at lunch time, then   is number of seats that were not used at lunch time.
 
 C.
A librarian had 150 books to be placed on shelves with an equal number of books on each shelf. If k is the number of shelves to be used, then   is the